[XS] Change in coreboot[main]: src/arch/x86/exit_car: Add proper x86_64 code

[Benjamin Doron (Code Review)]

Attention is currently required from: Jérémy Compostella, Patrick Rudolph.

Hello Patrick Rudolph,

I'd like you to do a code review.
Please visit

https://review.coreboot.org/c/coreboot/+/79162?usp=email

to review the following change.

Change subject: src/arch/x86/exit_car: Add proper x86_64 code
......................................................................

src/arch/x86/exit_car: Add proper x86_64 code

Don't truncate upper bits in assembly code and thus allow loading
of postcar stage above 4GiB.

Tested on qemu with cbmem_top set to TOUUD.

Change-Id: I42d1086f1220e44076ccf613244fc3c6d804805b
Signed-off-by: Patrick Rudolph 
---
M src/arch/x86/exit_car.S
1 file changed, 6 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/62/79162/1

diff --git a/src/arch/x86/exit_car.S b/src/arch/x86/exit_car.S
index c9ff866..d435dbe 100644
--- a/src/arch/x86/exit_car.S
+++ b/src/arch/x86/exit_car.S
@@ -67,8 +67,14 @@
    invd

movl	$_estack, %esp
+#if ENV_X86_64
+	/* Align stack to 16 bytes at call instruction. */
+	movq	$0xfffffffffffffff0, %rax
+	and	%rax, %rsp
+#else
    /* Align stack to 16 bytes at call instruction. */
    andl	$0xfffffff0, %esp
+#endif

/* Call this in assembly as some platforms like to mess with the bootflow and
       call into main directly from chipset_teardown_car. */